If you dont want to write your dream down as soon as you wake up, then heres what I usually do...

Just think through the dream as well as you can remember it. Tell it to somebody... I mean, not out loud, and not to anybody really, but rehearse it as if you're telling it to a friend. Subvocally, ya know?

This will fix the details in your mind and later in the day when youre awake enough to write you should be able to remember it. It works for me anyway.